When engaging the brakes of a vehicle, sometimes so called brake squeal is created. This effect is something that occurs both where disc and drum brakes are concerned. Typical frequencies of this noise are around a few kHz and within the sensitivity range of human hearing. The squeal noise that is produced decreases as the distance increases from the sound source, but can still be approximately 140 dB when close to the braking device. Most people will appreciate that city buses which stop at frequent intervals within densely populated areas, can be particularly disturbing. One frequent reason for complaint on new private cars, lorries and buses is brake squeal, including in association with ABS-braking systems. Even if brake squeal does not influence the braking power, and in turn safety, the problem is still of great importance because it is annoying to the customer, and therefore merits solution.
The problem of brake squeal has been analyzed many times, and many different solutions have been tested. For example, it has been tried to dimension the components included in brake systems in order to obtain a changed natural frequency of the system, but these attempts have not been able to reduce the occurrence of brake squeal in braking systems.
For example, U.S. Pat. No. 5,145,037 discloses a disc brake where the occurrence of brake squeal is intended to be reduced by means of beveling end regions of the brake disc within a region, the extension of which is dependent on the width between claws included in a brake yoke carrying a backing plate where the brake lining is arranged.
Furthermore, from GB 2143919 a disc brake is known where brake squeal is intended to be reduced by means of designing a backing plate included in the disc brake with an inclination in relation to the brake disc included in the disc brake.
Even if the above-mentioned suggestions, in certain predetermined conditions, are instrumental in reducing the occurrence of brake squeal, these solutions do not reduce the occurrence of brake squeal when applying a fluctuating load onto the brake member.